Contractile article and process of making same



Patented June 15, 1954 CONTRACTILE Nicolas Drisch and Rene Fays',

ARTICLE .AND PROCESS OF G SAME Paris, France, as-

signors to Societe Novacel, Paris, France, a corporation of France No Drawing.. Application March 14, 1952,

Serial No. 276,675

Claims priority, application France March 19, 1951 7 Claims.

This invention relates to a method for making contractile articles such as covers or caps for bottles and has for an object to provide a cap of the above type, which, after performing, is stretchable for application to the bottle, contracts onto the bottle neck and dries in situ to a permanent gel form.

Another object is to provide a cap which can be stored in the dry state, re-swells upon wetting so that it may be readily applied to the bottle, and finally dries to a permanent gel form.

Another object is to provide a cap of .the above type having substantial elasticity in the wet state.

Cellulose covers are known which shrink on drying. However, this shrinkage is quite limited and, after the cover has been positioned on the neck of the bottle to be capped, it is necessary to eiTect an initial drying in order to cause the cover to adhere sufficiently for the bottle to be handled.

Cellulose covers are distributed commercially in two forms; in a moist and distended condition and immersed in a wetting liquid, or dried and containing a plasticiser. In the latter case, it is necessary to cause the covers to swell again in an aqueous liquid before they can be used. This swelling is eiiected quite easily, owing to. the fact that the covers have a basis of cellulose and contain a plasticiser. Once the cellulose .covers have dried on the bottles, unauthorised opening of the bottles is-only possible with difiiculty, that is, it is only with difiiculty that the covers can be removed without damaging them.

It has also been proposed to employ covers having a basis of cellulose derivatives and which shrink on drying. These are distributed commercially only as moist covers in the form of a gel, in which the re-swelling is found to be too difiicult. When these cellulose derivative covers contain certain quantities of suitable products imparting elasticity, theyhave an appreciable elasticity, as described in U. S. Patent No. 2,645; 818, dated July 21, v1953, and U. 3. Patent No. 2,320,381, dated June. .1, 1943. This elasticity facilitates the fittingand eliminates the necessity for partial dryingof the covers before handling the cappedbottles.

Gelatine covers are also known, but the use of such covers presents scarcely any advantage over the cellulose covers. They are sensitive to moisture and have little elasticity.

Elastic covers proper. for example, made of rubber, have already been proposed, but the disadvantage of using such covers is that. their elasticity is permanent and for this reason they cannot prevent unauthorised opening.

There also exists covers which shrink on heat treatment, for example covers having a basis of certain thermoplastic resins. These covers are more or less elastic and may in certainv cases be fitted similarly to a rubber cover, but they necessitate a thermal treatment, that is, a supple inentary treatment, before they are set'in such condition that they prevent unauthorised opening of the bottles.

Finally, shrinkable covers have been proposed which have a temporary elasticity which permits them to be fitted easily by extension. These covers immediately adhere to bottle necks of varying dimensions within wide limits :and lose their elasticity on drying slowly while the capped bottles are stored, it being possible to place these bottles in the shop immediatelyafter the covers are fitted. Very useful'results have been obtained in this connection, especiallyusing polyvinyl formals.

However, the aforesaid shrinkable covers have hitherto been of the moist type, that is, asmentioned above, they are kept, until they are used, in an aqueous liquid which may contain acertain percentage of a plasticiser, an agent-giving them temporary elasticityand possibly anantiseptic agent. A preliminary drying of the: polyvinyl formal covers has hitherto not been successful because they then become-difiicult to re-swell whenit is required to put them into use.

According to the present invention, contractile covers in the form of polyvinyl formal gels are dried at low temperature andv therer'are ithus obtained covers which re-swells very easily in aqueous solutions of certain: products" having propertieswhich will be hereinafter defined.

Drying'tests carried out atdiiferent .tempera tures with: shrinkable covers of polyvinyl formals obtained in accordance: with U. S. PatentNo.

2,645,818, dated July 21, 1953, and U. S. Patent No. 2,320,381, dated June 1, 1943, have given the following results:

Therefore, drying carried out in the region of C. at normal pressure, and also drying under vacuum carried out in the region of 0., are found to be satisfactory, but it is quite obvious that these figures are in no respect limitative. It must be added that it is readily possible to employ combinations such as drying under partially reduced pressure at an intermediate temperature.

It is to be noted that the initial degree of swelling was 200%, that is, the cover initially contained 200% of water with respect to the base material.

It will be observed that the low-temperature drying considerably reduces the contraction and preserves the degree of re-swelling in an aqueous medium, viz.: the quantity of water in relation to the base material, after wetting again in aqueous medium.

The study of polyvinyl formal covers dried at low temperature shows that they are reticular membranes, that is, the cover has an obvious reticular structure. The swelling medium (water) has been replaced by pores filled with air. It may in fact be seen that the density of the covers dried at low temperature is of the order of 1, while the material itself has a specific gravity of 1.23. On the other hand, on re-wetting by immersion, small air bubbles are seen to escape. The re-wett-ed covers may be dried again at low temperature without affecting the degree of re-swelling in aqueous medium.

The low-temperature drying may be carried out at room temperature at normal pressure, for example, by blowing or drawing air through a layer of covers on a fixed or movable grid,'and it is possible to dry under vacuum at a slightly higher temperature. According to a modification, it is also possible first of all to displace the water by a neutral light solvent miscible in water, and then to evaporate this solvent at low temperature. The final result is approximately identical, i. e. the Xerogel of polyvinyl formal. It is also to be noted that the process is applicable to covers of other plastic materials obtained by wet coagulation, for example, cellulose triester covers.

The polyvinyl formal covers dried at low temperatures are more or less dull and opaque, but

when they have swollen again and then dried on a support, they become shiny, smooth and transparent;

The presence of white or colored pigments in the covers does not affect the drying according to the process described.

Aqueous gels obtained by cooling to room temperature a deposit formed from a hot solution of polyvinyl formals in solvents active only whenhot, .and thoroughly washing with water are particularly suitable. They may then be dried at low temperature as above stated.

The polyvinyl formal covers, dried at low tem perature, are re-swollen practically to the condition before their drying, as outlined above, by immersion in an aqueous liquid. Water may be used, but in order to give the re-swollen covers a pronounced elasticity, it is convenient to add certain products to the water, although the polyvinyl formal is in itself already plastic. They may be divided into two groups according to the boiling point at atmospheric pressure.

1. The products more volatile than water are eliminated before or with the water during the final drying of the fitted cover.

2. The products less volatile than water are eliminated in part only with the water during the final drying of the fitted cover.

In the last case, a part of the product remains in the cover after the said drying, at least for a certain time, according to its volatility.

The products to be used must satisfy a certain number of conditions, in addition to that con sidered above:

(a) Be soluble in water,

(12) Be capable of being readily absorbed from the aqueous medium by the polyvinyl formal, thus giving the aqueous gel of the formal its elastic character,

(0) Be sufficiently stable in aqueous medium,

((1) Not be toxic or corrosive,

(6) Be non-hygroscopic,

(I) Have very little odor,

(g) Be insensitive to mould growth.

' tion, carried out with the known stretching devices.

There is preferably employed an 8%-10% solution of methylglycol adipate containing, for example, 5% glycol diacetate (calculated with respect to the adipate). Y

It is, however, to be understood that the process which has been described is in no way limitative and that any modification in the same spirit also comes within the scope of the invention.

Thus, the reticular membranes obtained in accordance with the present invention may constitute, after re-swelling, excellent dialysis membranes for uses such'as those described in French Patent No. 969,911 of the 26th of July, 1948 for Dialysant Membranes.

What is claimed is:

1. The vmethod of making retractile articles such as caps and bands having sufficient elasticity in the moist or gel state to permit stretching thereof, which comprises forming a depositof a hot solution of water insoluble polyvinyl formal in a solvent active only when hot, cooling the deposit to room temperature to form a gel con taining about 200% of water, washing with water, and drying at a temperature below about 45 C. to substantially remove the water and form a dry reticular gel containing pores having" a volume such that the'specific gravity ofthe' membrane is about 1 and is capable of taking up water to a water content of at least 165% when soaked in an aqueous medium.

2. A dry bottle cap comprising a reticular membrane composed of water insoluble polyvinyl formal, said cap containing pores having a volume such that the specific gravity of the membrane is about 1 and being capable of taking up water to a Water content of at least 165%.

3. The method set forth in claim 1 in which the gel is dried at a temperature of about 20 C. at atmospheric pressure.

4. The method set forth in claim 1 in which the gel is dried at a temperature of about 30 C. under a vacuum of about 65 cm. of mercury.

5. In the method set forth in claim 1 the additional step which comprises soaking said gel in an aqueous medium containing a product less volatile than Water and capable of imparting elasticity by absorption from the aqueous me dium.

6. The method set forth in claim 5 in which aqueous solu- References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 2,077,298 Zelger Apr. 13, 1937 2,222,490 Robertson Nov. 19, 1940 2,236,061 Izard et a1. Mar. 25, 1941 2,311,059 Lowe Feb. 16, 1943 2,338,787 Ushakoff Jan. 11, 1944 2,435,239 Schub Feb. 3, 1948 2,512,490 Drisch et a1. June 20, 1950 2,576,820 Barnes et a1 Nov. 27, 1951 OTHER REFERENCES Soc. de la Viscose Francaise, French patent of addition 54,103, February 10, 1947. 

1. THE METHOD OF MAKING RETRACTILE ARTICLES SUCH AS CAPS AND BANDS HAVING SUFFICIENT ELASTICITY IN THE MOIST OR GEL STATE TO PERMIT STRETCHING THEREOF, WHICH COMPRISES FORMING A DEPOSIT OF A HOT SOLUTION OF WATER INSOLUBLE POLYVINYL FORMAL IN A SOLVENT ACTIVE ONLY WHEN HOT, COOLING THE DEPOSIT TO ROOM TEMPERATURE TO FORM A GEL CONTAINING ABOUT 200% OF WATER, WASHING WITH WATER, AND DRYING AT A TEMPERATURE BELOW ABOUT 45* C. TO SUBSTANTIALLY REMOVE THE WATER AND FORM A DRY RETICULAR GEL CONTAINING PORES HAVING A VOLUME SUCH THAT THE SPECIFIC GRAVITY OF THE MEMBRANE IS ABOUT 1 AND IS CAPABLE OF TAKING UP WATER TO A WATER CONTENT OF AT LEAST 165% WHEN SOAKED IN AN AQUEOUS MEDIUM. 